1. Field of the Invention
The present invention relates to a chemical vapor deposited film formed by the plasma CVD method and a layered body, thin-film solar cells that comprise the same, and a manufacturing method for the layered body.
2. Background Information
In recent years, regarding display devices using organic EL, liquid crystal, etc., the methods for weight reduction and making thin film, as well as, from the point of view of making them flexible, methods to use plastic sheets or plastic film as the base material have been developed and proposed. From the point of view of maintaining the visibility of the display unit and preventing oxidation and deterioration of the element part that is formed on the surface of the base material, a gas barrier film having gas barrier properties with extremely high oxygen and vapor barrier properties is in demand. Additionally, regarding solar cells, from the point of view of preventing the degradation of the power generation layer and the electrodes, etc., and prolonging the lifetime, a gas barrier film that has both high gas barrier properties and flexibility is in demand.
A method to form a gas barrier film with high gas barrier properties by the plasma CVD method using a layered structure of an organic layer and an inorganic layer, or two inorganic layers, has become common.
Patent Document 1 (Japanese Laid-Open Patent Application Publication No. H5-345383) proposes forming a polymer-coated layer consisting of silicon (Si), carbon (C), and oxygen (O) as the first layer and a silicon oxide compound layer represented by SiOX (X=1.5-2.0) as the second layer as a method to form a barrier film with strong adhesion and high barrier properties on a plastic base material surface using the plasma CVD method. Patent Document 2 (Japanese Laid-Open Patent Application Publication No. 2005-097678) also proposes forming an adhesion reinforcing layer consisting of silicon (Si), carbon (C), and oxygen (O) as the first layer and a barrier film consisting of silicon oxide as the second layer as a method to form a barrier film with strong adhesion and high barrier properties on a base material surface such as plastic vessels, using the plasma CVD method.
However, while the above-described barrier film will exhibit good adhesion to a base material of a single plastic, adhesion to a base material in which plastic (an organic substance) and metal (an inorganic substance) are mixed onto a surface that forms a barrier film, such as organic EL elements and solar cells, etc., which are weak against moisture and oxygen, is insufficient; additionally, a film consisting of only silicon (Si), carbon (C), and oxygen (O) is, in general, highly dense and lacks flexibility, so there was a problem that breaking the barrier film was likely to occur.
Patent Document 3 (Japanese Laid-Open Patent Application Publication No. 2007-262551) discloses that a silicon-based thin film having strong adhesion and high barrier properties can be formed by forming a first thin film by the plasma CVD method on a plastic film or an electronic device, such as organic EL, etc., using a gas comprising hydrogen atoms and a gas comprising silicon atoms, and forming a second thin film with a barrier function on the first thin film. Specifically, a film is formed using hexamethyldisilazane (hereinafter sometimes referred to as HMDS), which is an organic silicon-based compound that does not comprise oxygen atoms, and a mixed gas of H2 and Ar. However, with this film, adhesion with an especially transparent conductive film and metal film that exist in organic EL elements and solar cells, etc., was insufficient, so there was the problem that breaking the barrier film was likely to occur.
Also, as a well-known method, there is a method to improve the adhesion between the barrier film and the base material by irradiating plasma to the base material before forming the barrier film in order to activate and modify the surface, as disclosed in Non-Patent Literature 1 (Surface Technology Vol. 58 (2007), No. 5, p. 260-p. 266), p. 262, lines 18-25. However, this generates significant deterioration (oxidation degradation, etc.) of the base material with organic EL elements and solar cells, etc.; therefore, this method could not be used.